Bipolar electrosurgical forceps

ABSTRACT

A bioplar electrosurgical forceps carries a thermocouple junction at the distal end of each of two mutually opposed prongs. The junctions are formed by welding a constantan wire directly to the ferrous metal prongs, thereby avoiding the need for electrical isolation.

BACKGROUND OF THE INVENTION

1. Field:

The present invention relates to electrosurgical apparatus of the typetypically used in surgical operations for coagulating biological tissue,and provides a device for use with such electrosurgical apparatus.

2. State of the Art:

Electrosurgery is a known technique for performing cutting andcoagulation procedures during surgical operations. Radio frequency (rf)current supplied by an electrosurgical generator is conveyed to apatient through the use of specialized electrodes. For example, a pairof such electrodes may be formed as opposing prongs or legs of a bipolarforceps. Reliable control of the temperature of each prong is essential.Otherwise, when the prongs are used for coagulation, tissue adhesionsmay result; particularly if one of the prongs is inserted further intothe biological tissue than is the other prong. In such instances, theprong that is inserted to a lesser extent tends to become hotter,thereby increasing the risk of adhesions at its contact tip. If thetemperature at a prong rises to above 80° C., the forceps may actuallybecome destructive of a surgical procedure which the coagulationprocedure is intended to support.

To minimize the likelihood of overheating, it has been suggested toplace temperature sensors near the contacting face of the coagulatinginstrument. For example, U.S. Pat. No. 4,685,459 suggests embeddingthermocouples as thermosensors in the machined tips of a coagulatingforceps. This type of construction is relatively expensive tomanufacture. Because the thermocouple is separated by insulation fromthe forceps, the response time of the device is reduced. Moreover, thedevice is inherently susceptible to the problems associated withbreakdown of the electrical insulation between the thermocouple andforceps.

U.S. Pat. No. 3,685,518 discloses a surgical forceps designed to preventthe terminal parts of the forcep jaws from overheating. The disclosureof U.S. Pat. No. 3,685,518 is incorporated by reference in thisdisclosure for its description of bipolar high frequency surgicaldevices, the hazard of overheating associated with the use of suchdevices, and the importance of materials selection and configuration ofparts in the design of such instruments.

U.S. Pat. No. 4,041,952 discloses an electrosurgical forceps withmechanical switching means carried by the tines (legs) of a forceps.Electrosurgical energy is applied to the contact surfaces (tips) of thetines by finger pressure applied to the tines to close the associatedswitching means.

U.S. Pat. 4,662,369 discloses a safety circuit for an electrosurgicalapparatus. The circuit functions to sense rf current leakage and torespond by redirecting the output of the rf source (generator), therebyto limit leakage to below a predetermined value. The disclosure of U.S.Pat. 4,662,369 is incorporated by reference in this disclosure for itsgeneral description of electrosurgical techniques and the hazardinherent to such techniques of electrical burns.

U.S. Pats. 4,671,274; the aforesaid 4,685,459 and 4,686,908 are eachdirected to bipolar electrosurgical instruments of specialized design.These patents, the disclosures of which are incorporated by reference asa part of this disclosure, describe the components and uses ofinstruments of this type.

A number of instruments currently supplied by F. L. Fischer, Fischer METGmbH, Schopfheimer Str, D0-7800 Freiburg, Federal Republic of Germany,are disclosed in a brochure entitled "New Dimensions in BipolarCoagulation." The brochure describes an rf generator and associated handpieces which purportedly eliminate burns and tissue sticking to theinstrument tips. Thermosensors are integrated in the tips of thecoagulation instrument to continuously measure the contact temperaturesbetween tissue and metal. Microprocessors continuously respond to ensurethat the temperature remains constant throughout the coagulationprocedure.

In spite of the advances in electrosurgical techniques reported by theaforedescribed patents and commercial instruments, there remains a needin the electrosurgical art for an improved temperature sensing forceps.In particular, there remains a need for such an instrument which avoidsthe problems associated with electrically insulating thermocoupleelements from rf-carrying prongs (legs, tines) of the forceps. Thetemperature-controlled (sensing) forceps available currently remainexpensive and difficult to manufacture, are characterized by delayedresponse of the thermocouple elements by virtue of the insulatingmaterial, and are susceptible to electrical breakdown (of theinsulation) between the thermocouple elements and the prongs.

SUMMARY OF THE INVENTION

The instant invention comprises a structural arrangement of componentswhich both simplifies and improves over bipolar forceps devices of thetype represented by U.S. Pat. No. 4,685,459. A significant feature ofthis invention is the reliance upon the material of construction of eachprong of the forceps as one of the elements of a thermocouple junctionat the distal end of the prong. Only one wire need thus be extended thelength of the prong to the thermocouple junction. The burdensomemanufacturing requirements imposed upon prior art devices by the need tophysically isolate (with insulating materials) the thermocouple from therf prongs is avoided.

The electrosurgical apparatus of this invention includes an rf generatorwith the general electrical characteristics of such generators utilizedpreviously for electrosurgical applications. Such generators deliver rfenergy at a bipolar output. The apparatus further includes a bipolarforceps with two individual rf-carrying prongs, electrically isolatedfrom each other and electrically connected, e.g. through a transformerto the rf output of the generator. In effect, each prong of the forcepsmay be viewed as an extension of one of the bipolar elements of the rfoutput of the generator. The forceps includes a proximal end, adapted tobe grasped by the fingers of an operator, and a distal or working end.Electrical isolation of the prongs is provided at the proximal end ofthe forceps by insulating material and for the remainder of the lengthof the forceps by physical separation. Finger pressure applied to theprongs at an intermediate location reduces the spacing at their distalends in conventional fashion. The prongs are typically fashioned fromferrous material; e.g. surgical or stainless steel.

The distal end of each prong carries a thermocouple junction formed byjoining; e.g., by spot welding a dissimilar metal (typically constantan)directly to the prong. A pair of leads connect the junction of therespective prongs to respective measuring circuits. The measuringcircuits are electronically isolated, ideally in complete bipolarisolation from the rf energy circuits, specifically including therf-carrying prongs themselves.

Both the rf generator, with its prong extensions and the measuringcircuits, with their thermocouple components, may be electronicallyconnected to appropriate computing circuitry such as that provided by acentral processing unit (C('U). In particular, it is desirable toincorporate display and signal means in association with the computingcircuits and the measuring circuits. In this fashion, an audible alarmor other signal can be generated in response to non-nominal conditionsdetected by the thermocouples. For example, it may be crucial for asurgeon to become instantly aware if the temperature at the distal endof either prong rises beyond a preselected temperature (e.g. 78° C.).Alternatively, the computing circuitry may function to attenuate thepower output of the rf generator under such conditions, thereby tomaintain the appropriate temperature.

DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate what is presently regarded as the bestmode for carrying out the invention:

FIG. 1 is a schematic diagram of an embodiment of the invention;

FIG. 2 is a top plan view of a hand device for use with electrosurgicalapparatus made in accordance with the present invention;

FIG. 3 is a side elevational view of the device of FIG. 2;

FIG. 4 is a cross-sectional view of the device of FIG. 2, taken alongthe reference line 4--4 of FIG. 3;

FIG. 5 is a cross-sectional view of the device of FIG. 2 taken along thereference line 5--5;

FIG. 6 is a cross-sectional view of the device of FIG. 2 taken along thereference line 6--6; and

FIG. 7 is a schematic diagram of an alternative embodiment of theinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring to FIG. 1, there is schematically illustrated anelectrosurgical apparatus 10 and a hand-held device 12 for use withapparatus 10. The apparatus 10 includes an rf generator 14 which may beselected from among the radio frequency generators presently included incommercially available electrosurgical devices. The rf generator 14produces a radio frequency which is supplied to output connection ports16, 17 by wires 19, 21. Hand-held device 12 is electrically connected toconnection ports 16, 17 by wires 23, 25, respectively, throughappropriate connectors (not shown). A conventional central processingunit (CPU) 30 is connected in circuit to the rf generator 14 ininteraction with measurement and display functions, as shown. Device 12comprises a pair of prongs 28, 29 which are electrically insulated fromeach other by an insulating retaining member 31.

FIGS. 2 through 6 illustrate in more detail the device 12 of the presentinvention. The prongs 28, 29 (FIG. 2) are firmly placed within retainingmember 31. Wire 23 is electrically connected to prong 28 and wire 25 iselectrically connected to prong 29. Prongs 28, 29 are identical inconstruction. Accordingly, only prong 28 need be discussed in de&:ail,it being understood that the other prong 29 is similarly constructed.

Prong 28 comprises an elongated central member 32 made of a materialcapable of transmitting an rf frequency. The proximal end 34 of member32 is electrically connected to wire 23, e.g. by welding as illustrated(FIG. 5). The distal end 35 of the elongated contact member 32 carries acontact surface 36 which is configurated for placement againstbiological tissue for application of rf frequency current. The elongatedmember 32 is provided with an exterior insulating coating 38, to protectthe hand of an operator clasping the pair of prongs 28, 29. One suitablecoating 38 comprises nylon, which may be applied by an appropriatedipping process. The elongated member 32 is provided with alongitudinal, axially extending groove 42 which accommodates aninsulated wire 44. The insulated wire 44 comprises a wire core 45surrounded by an appropriate insulation layer 46. The insulation layer46 is stripped away so that the bare wire 45 is exposed for welding at ajunction 50 to elongated member 32. The elongated member 32 and wire 45are made of different materials selected such that the junction 50 formsa thermocouple. A suitable such junction 50 results when the wire 45 isof constantan and the elongated member 32 is of stainless steel. Wire 45is electrically connected to apparatus 10 at inlet port 57 (FIG. 1) byan appropriate connector (not shown). The corresponding wire 45 of prong29 is electrically connected to inlet port 59 in the same fashion.

In operation, the rf generator 14 applies an appropriate rf frequencycurrent through wires 19, 21, 23, 25 to prongs 28, 29. The contact tips36 of prongs 28, 29 apply the rf energy to biological tissue (not shown)to be treated. The thermocouple junctions 50 produce respectivethermocouple measuring signals which are indicative of the temperaturesof respective contact surfaces 36.

Means for isolating the rf frequency signal from the thermocouple signalfor each prong 28, 29 in the embodiment illustrated in FIG. 1 comprisesa pair of radio frequency chokes and a capacitor. Rf choke L1, rf chokeL2 and capacitor C1 are associated with prong 28. One end of choke L1 isconnected through input wire 19 to the elongated member 32. One end ofchoke L2 is connected through the wire 45 to a junction 50. The otherend of chokes L1 and L2 are connected to opposite sides of the capacitorC1. The thermocouple signal of prong 29 is similarly separated from therf frequency signal by corresponding components, rf chokes L3, L4,capacitor C2, and isolating capacitors 60.

The capacitor C1 and chokes L1 and L2 are respectively connected to apreamplifier U1 for increasing the thermocouple signal. The output ofthe preamplifier U1 is connected to an isolation amplifier U2 whichbrings the output signal from the preamplifier U1 to ground potential,producing a digitized output signal. The output of the isolationamplifier U2 is connected to the central processing unit 30. The CPU 30is adapted to convert the thermocouple measuring signal, as delivered byamplifier U2, to a temperature measurement displayed as the left sidetemperature at DP1. For purposes of this disclosure, the prong 28 isregarded as the left side and the prong 29 is regarded as the rightside. Other indicating means may be provided in addition to or in placeof the temperature display DP1. For example, the CPU may be connected toan audio signal generator to produce a tone when a predeterminedtemperature is reached.

In similar fashion, chokes L3, L4 and capacitor C2 are connected throughpreamplifier U3, and an isolation amplifier U4, to the centralprocessing unit 30 where the thermocouple signal from the thermocouplejunction 50 on the right side (prong 29) is translated to a temperaturemeasurement. This temperature measurement is displayed as the right sidetemperature at DP2, as illustrated. Various other display means may beused either in addition to or in place of the visual display DP2 as inthe case of display DP1.

As illustrated, a third visual display DP3 is provided for displayingthe difference in temperature between the contact surface 36 of prong 28and the contact surface 36 of prong- 29. There is also illustrated anaudible alarm, controlled by CPU 30 to signal any temperaturedifferential regarded as undesirable.

The CPU can be programmed to adjust the output of the rf generator atleads 19, 21 as desired. In the particular embodiment illustrated, acontrol feedback signal is generated by the central processing unit 30to the rf generator 14 as indicated by line 61. In the preferredoperation of the present invention, the central processing unit 30 isprogrammed such that when the temperature of the contact surface 36 ofeither prong 28 or 29 rises above a predetermined temperature, the rfgenerator output will be adjusted appropriately so as to reduce thetemperature at the contact surface 36. This adjustment is typicallyeffected by lowering the energy supplied to wires 19, 21. For example, acentral processing unit 30 may be programmed such that a temperature inexcess of 80° C. at contact surface 36 induces a feedback signal tooccur, thereby adjusting the rf generator output. CPU 30 may beprogrammed such that when a predetermined differential between therespective contact surfaces 36 of prongs 28, 29 is obtained, the rfgenerator output either will be reduced until the temperaturedifferential is brought to within the desired limits, and/or it willshut off.

The device 12 is of simple construction and very durable. Because theelongated member 32 comprises one of the junctions of the thermocouple,it is not necessary to insulate the thermocouple as in previous devicesof this type. The absence of insulation between the thermocouplejunction 50 and the member 32 results in faster temperature response andavoids the hazard of breakdown of the insulation between thethermocouple and the prongs.

FIG. 7 is a generalized representation of the present invention, oneembodiment of which is that illustrated by FIG. 1. Measuring circuit M1and M2 are provided for converting the signals from junctions 50 ofprongs 28, 29 to temperature measurements. M1 and M2 may compriseamplifier driven optocoupler circuits, for example.

In the preferred embodiment, the circuitry for isolating thethermocouple measuring signal from the rf frequency is illustrated aspart of the electrosurgical apparatus 10. In practice, it may be moreconvenient for the isolating circuitry to be included in the hand-helddevice 12.

Reference herein to details of the illustrated embodiments is notintended to limit the scope of the claims which themselves recite thosefeatures regarded as important to the invention.

What is claimed:
 1. An electrosurgical apparatus comprising:an rfgenerator with first and second output terminals; a hand-held forcepsformed of first and second prongs, respectively, said prongs beingelectrically coupled to respective said terminals; each of said prongshaving a proximal end and a distal end formed of a first metal, saidprongs being positioned in approximately parallel spaced alignment withtheir proximal ends held in fixed non-conductive relationship and theirdistal ends spaced from each other in opposed working relationship; thedistal ends of said prongs respectively comprising surgical contactsurfaces electrically connected to said generator, and carrying athermocouple junction between said first metal and a second metal in agroove separated from said contact surfaces; conductors extending fromrespective said thermocouple junctions in mechanical association withbut in non-conductive relationship with respective said prongs; andmeasurement circuit means electronically associated with said conductorsto detect signals from respective said junctions and to convert saidsignals into respective temperature measurements, said measurementcircuit means being electronically isolated from said rf generator. 2.Apparatus according to claim 1 wherein each of said prongs is conductivebetween its proximal and distal ends and said conductors are formed ofsaid second metal.
 3. Apparatus according to claim 2 wherein saidproximal ends are held by an insulating fixture.
 4. Apparatus accordingto claim 3 wherein said prongs are made of ferrous metal and saidconductors are made from constantan metal.